PDF Tags

The tags listed in the PDF tables below are those which are used by ExifTool
to extract meta information, but they are only a small fraction of the total
number of available PDF tags. See
http://www.adobe.com/devnet/pdf/pdf_reference.html for the official PDF
specification.

ExifTool supports reading and writing PDF documents up to version 1.7
extension level 3, including support for RC4, AES-128 and AES-256
encryption. A Password option is provided to allow processing of
password-protected PDF files.

ExifTool may be used to write native PDF and XMP metadata to PDF files. It
uses an incremental update technique that has the advantages of being both
fast and reversible. The original PDF can be easily recovered by deleting
the PDF-update pseudo-group (with -PDF-update:all= on the command
line). However, there are two main disadvantages to this technique:

1) A linearized PDF file is no longer linearized after the update, so it
must be subsequently re-linearized if this is required.

2) All metadata edits are reversible. While this would normally be
considered an advantage, it is a potential security problem because old
information is never actually deleted from the file.

As well as the tags listed below, the PDF specification allows for
user-defined tags to exist in the Info dictionary. These tags, which should
have corresponding XMP-pdfx entries in the XMP of the PDF XML Metadata
object, are also extracted by ExifTool.

Writable specifies the value format, and may be string, date,
integer, real, boolean or name for PDF tags.

Tag ID

Tag Name

Writable

Values / Notes

'AAPL:Keywords'

AppleKeywords

string+

(keywords written by Apple utilities, although they seem to use PDF:Keywords
when reading)